# US 11,440,839 B2 · Optical fiber coating die with reduced wetted length > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,440,839 B2 - Document ID: US11440839B2 - Status: Granted - Kind: B2 - Application number: 17/112,166 - Filed: 2020-12-04 - Published: 2021-03-25 - Granted: 2022-09-13 - Earliest claimed: 2017-01-24 - Assignees: Corning Incorporated - Applicants: Corning Incorporated - Inventors: Sumitava De; Robert Clark Moore; Douglas Gregg Neilson; Pushkar Tandon - Web page: https://patentgrep.com/patent/US11440839B2 ## CPC - C03C 25/105: Organic claddings - C03C 25/18: Extrusion - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS ## Abstract An optical fiber coating apparatus that provides increased gyre stability and reduced gyre strength, thereby providing a more reliable coating application process during fiber drawing includes a cone-only coating die having a conical entrance portion with a tapered wall angled at a half angle α, wherein 2°≤α≤25°, and a cone height L1 less than 2.2 mm, and a cylindrical portion having an inner diameter of d2, wherein 0.1 mm≤d2≤0.5 mm and a cylindrical height of L2, wherein 0.05 mm≤L2≤1.25 mm; a guide die having an optical fiber exit, the guide die disposed adjacent the cone-only coating die such that a wetted length (L5) between the optical fiber exit of the guide die and the entrance of the cone-only coating die is from 1 mm to 5 mm; and a holder for holding the cone-only coating die and the guide die in a fixed relationship defining a coating chamber between the guide die and the cone-only coating die, the coating chamber having an inner radius L6 from the optical fiber axis to an inner wall of the holder that is from 3 mm to 10 mm. ## Claims ### Claim 1 A process of coating an optical fiber during a fiber draw process wherein the optical fiber is drawn at a draw speed Vd, and the process of coating the optical fiber, comprises: passing the drawn optical fiber through a guide die and thereafter through a cone-only coating die, the cone-only coating die having a wall temperature Tdie and a conical entrance with a tapered wall angled at a half angle α, wherein 2°≤α≤25°, and a cone height L1 less than 2.2 mm, and a cylindrical portion having an inner diameter of d2, wherein 0.1≤d2≤0.5 mm, and a cylindrical height of L2, wherein 0.05≤L2≤1.25 mm, the guide die having an optical fiber exit, the guide die disposed adjacent the cone-only coating die such that a wetted length L5 between the optical fiber exit of the guide die and the conical entrance of the cone-only coating die is less than 4.5 mm, the cone-only coating die and the guide die being held in a fixed relationship by a holder to define a coating chamber between the guide die and the cone-only coating die, the coating chamber having an inner radius L6 from the optical fiber to an inner wall of the holder that is from 3 mm to 10 mm, the coating chamber holding a liquid coating composition that is entrained on a surface of the optical fiber as it is drawn through the cone-only coating die resulting in coating thickness of dcoat on the surface of the optical fiber. ### Claim 2 (depends on 1) The process of claim 1, wherein the wetted length L5 is less than 3.5 mm. ### Claim 3 (depends on 1) The process of claim 1, wherein the inner radius L6 of the coating chamber is from 6 mm to 10 mm. ### Claim 4 (depends on 1) The process of claim 1, wherein the cone height L1 is between 0.25 mm and 2.0 mm. ### Claim 5 (depends on 1) The process of claim 1, wherein the draw speed Vd is larger than 45 m/s. ### Claim 6 (depends on 1) The process of claim 1, wherein the draw speed Vd is larger than 60 m/s. ### Claim 7 (depends on 1) The process of claim 1, wherein a ratio of wetted length L5 to draw speed Vd is between 0.01 msec to 0.15 msec. ### Claim 8 (depends on 7) The process of claim 7, wherein the ratio of wetted length L5 to draw speed Vd is between 0.025 msec to 0.125 msec. ### Claim 9 (depends on 1) The process of claim 1, wherein the thickness of the liquid coating composition on the surface of the optical fiber dcoat is between 2 microns and 50 microns. ### Claim 10 (depends on 1) The process of claim 1, wherein the liquid coating composition that is entrained on a surface of the optical fiber is a UV curable acrylate composition and is cured using a light emitting diode UV source having an emission spectrum with a peak wavelength in the range between 300 nm-450 nm. ### Claim 11 (depends on 1) The process of claim 1, wherein the cone-only coating die is a primary coating die and the liquid coating composition that is entrained on a surface of the optical fiber is a primary coating and the thickness of the liquid primary coating composition on the surface of the optical fiber dcoat is between 10 microns and 50 microns. ### Claim 12 (depends on 1) The process of claim 1, wherein the cone-only coating die is a secondary coating die and the liquid coating composition that is entrained on a surface of the optical fiber is a secondary coating and the thickness of the liquid secondary coating composition on the surface of the optical fiber dcoat is between 10 microns and 50 microns. ### Claim 13 (depends on 1) The process of claim 1, wherein the cone-only coating die has a lubrication pressure that is less than 500 psi. ### Claim 14 (depends on 1) The process of claim 1, wherein a gyre is formed in the coating chamber having a maximum temperature of less than 175° C. ### Claim 15 (depends on 14) The process of claim 14, wherein the maximum temperature of the gyre is less than 100° C.